The finds are among many historic artefacts dating back to the Bronze Age unearthed by a 12-strong team of archaeologists working at the site of the Highways Agency’s A11 dualling scheme near Thetford.

Pottery, flint tools, coins, metal and animal bones dating back to 4,000BC have been discovered, while evidence has also been found of settlements that have stood at the site since 1,500BC, including a Roman farmstead.

Mr Pankhurst said the lock dated back to the Roman era and was likely to have been hammered into shape from iron at a forge, while the Romans were fond of oysters, which they fished from the Norfolk and Suffolk coast.

He believed the site, measuring one-and-a-half kilometres in length, was likely to have been home to six or seven homes, built using posts in the ground, during the Roman era and was chosen because the fertile land was ideal for growing crops.

Etched in the ground is the outline of a clay building where kilns were used to dry corn to make bread and the black charring left by the furnaces is still evident in the clay soil.

The bones of cows, sheep and horses butchered by the inhabitants can also be found all over the site between Chalk Hall Farm and the B1106 near the How Hill Tumulus.

Evidence has also been found of cremations on the northern part of the site, while human remains were also found in a grave separated from the main farmstead, causing speculation among the archaeologists as to why that might have been the case.

Mr Pankhurst said: “The great thing is that we normally only get to see a little bit of a window onto it, but this work has revealed a lot.”

The 23 week pre-construction survey carried out by Pre-Construct Archaeology is part of planned work on the site prior to the start of work to dual the last remaining single carriageway section of the A11 in January.

The scheme will see 5.5 miles of the A11, between Thetford and the Fiveways roundabout near Barton Mills, widened and a new 3.6 mile bypass built around the village of Elveden.

Some of the artefacts have been sent to scientists to determine their exact origins.

The Highways Agency has said the new bypass and widening of the A11 will bring significant benefits for the economy, road users, and local people, by improving road safety and removing traffic bottlenecks.